The use of double wall pipe is becoming more and more popular and these pipes which can vary tremendously in size have many benefits over pipes having a single wall construction.
Extrusion dies for forming double wall pipes have been available on the market for some time now. Although the design of these dies may vary from one manufacturer to another, they all typically include an upstream injector which feeds plastic to parallel spaced apart plastic flow lines from which the plastic is extruded to form inner and outer pipe walls. These pipes may have smooth walls or they may have different configurations, such as a ribbed wall or the like.
In many applications, virgin material is required even though less expensive recycled material is available. However, due to its inherent make-up, this recycled material will not provide certain requirements, such as chemical stability and smoothness in the pipe wall. Furthermore, it is very difficult to introduce coloring to a conventionally formed double wall pipe. Wall coloring of the pipe can be very useful for things such as pipe identification purposes, and the like.